Device for recovering cores from boreholes



Patented Nov. 5, 1940 UNITED STATES PATENT OFFICE DEVICE FOR RECOVERING CORES FROM BOREI-IOLES Alphons Gerard Hubert Straatman, The Hague, Netherlands, assignor to Shell Development Company, San Francisco, Calif., a corporation of Delaware Application January 26, 1937, serial No. 122,348 In the Netherlands February 8, 1936 Claims.

5 the necessity of removing or raisingthe drilling equipment from the borehole.

There has been described in the U( S. Letters Patent No. 2,073,263 to Hohmann and De Wilde, i a device comprising a core barrel fitting inside a drill bit and surrounded bya valved annular passage, by means of which device 'cores can be lifted to the surface by the pressure of the drilling fluid. For this purpose, the circulation of the drilling fluid, which is normally pumped down through the drill pipe, is reversed by pumping said fluid down outside the drill pipe, whereby the valved annular passage is automatically closed, and the.

pressure of the drilling fluid, applied to the bottom face of the core, operates to raise the core and the core barrel to the 4surface through the drill pipe.

It has'been, however,` found that apparatus of this construction gives rise in operation to various diculties due to the scoring and clogging of the Vautomatic valve located in the relatively constricted annular passage between the core drill and the core barrel and subjected to the pressure of the drilling uid.

It is the object of Vthe present invention to' remedy these diiiculties by providing a core lifting apparatus arranged so that the surface subjected to the pressure of the reversed drilling uid is formed by a packer or piston located above the core barrel.

It isv another object-of this invention to provide a core lifting apparatus either ,entirely dispensing with a valve controlling the directional flow of the drilling fluid-or having a valve attached to the core barrel instead of the drill pipe or bit,

whereby said valve is lifted to the wsurface during each core-taking operation and; may be easily repaired if damaged, or cleaned if clogged.

Other objects and features of the invention will appear more clearly from the following description taken in connection with the attached drawing, wherein:

' Figs.- la and 1b give a` cross-sectional elevation 50 view of a preferred embodiment of the present invention in which the surface subjected to the pressure of the drilling fluid is formed by a piston permanently attached to the core barrel.

Fig. 2 gives a cross-sectional elevation view of a part of another preferred embodiment of the (Cl. Z55-'12) present invention in which said piston forms part of a separate hoisting device lowered into the well and temporarily coupled to thefcore barrel when the latter is to be lifted from the well.

Referring to Fig. 1, a drill pipe comprising 5 coupled sections I, I2 and 25 is shown carrying at its lower end a drill bit 28,.provided with suitable passages 2'I for the circulation of the drilling iluid. The drill bit has a circular opening 29 at its lower end to receive the core. A bushing l0 3|, carrying suitable core-catching members 32,

is inserted in this opening and screwed to the drill bit. The bushing 3I is provided with a shoulder 30. The lower end of a core barrel 25 lits slidingly against said shoulder. The core bar- 15. rel 25 is closed at the top by a barrel head 2I, provided with a vent valve 20. A hollow mandrel I6 is screwed to the head 2| and carries a plurality of pawls I4 (of which one is shown in the cross sectional drawing), rotatable about shafts I5. The pawls I4 abut with their upper ends against the sloped inside shoulder of a collar I3 attached to the drill pipe. When in the position shown 'in the drawing, these pawls prevent an 25 upper' movement of the core barrel. They are forced into said position by the thickened portion II of a rod IIA which ts slidingly in the axial bore of the mandrel I6 and carries atits lower end a stop nut I l. Above its thickened 30 portion II, the rod IIA extends as a tube I0, which forms in its upper part a housing for a ball valve l. The ball is pressed upwards by a spring 9 against a seat'I which is fitted in a tubular part 5 screwed into the tube ID. The 35 tubular part 5 carries externally a packer or piston 4 made of rubber, canvas or other suitable elastic material, and adapted to t tightly against the walls of the drill pipe I. The tubular part 5 is closed at the top by a head 2 provided with lat- 40 eral openings 3. y

In operation, the following prpced'ure may be followed:

When the core is being drilled, the position of the parts is as shown on the drawing. The drilling fluid is pumped down inside the drill pipe I and passesthrough the lateral openings 3 in the head 2, inside the tubular part 5, past valve 1, which is forced down against the action of spring 9, around tube Ill and mandrel I6 to the annular space betweendrill pipe section I2 and core barrel 25, being finally discharged to the outside of the drill pipe through passages 21 ln the drill bit.

When the circulation is reversed, and the drill- I the nut I1.

thickened rod I I permits the pawls I4 to move ining fluid is pumped down outside the drill pipe, it enters the latter through the passages 21, and passes up through the annular space between the inside walls of the drill pipe and the core barrel and the mandrel I6. The ball valve 1 is now, however, pressed against the seat 6 by the action of spring 9, thus preventing further escape of the uid. The pressure of the fluid, acting on the underside of piston 4 causes the latter to move upwards, carrying with it the tube I0 and the rod II-I IA, until said motion is stopped by The upward displacement of the wards by pressure against. the slanting shoulder I3, whereby the whole core barrel assembly is released from engagement with the drill pipe and lifted to the surface by the continued fluid pressure against the piston 4 and/or the bottom of the core.

If the piston 4 is to be effective in raising the core barrel assembly to the surface, it is desirable that it should remain in continuous contact with the walls of the drill pipe throughout the whole length of the string. Tool joints free of internal constructions, that is, tool joints of the externally upset type should, therefore, be preferably use d to connect drill pipe sections when using the apparatus of this invention.

It is, however, possible to use the present corelifting device in drill pipe strings equipped with the usual internally upset tool joints and having, therefore, passages of reduced diameter at the couplings, provided the length of the core barrel assembly (from piston 4 to the lower end of the core barrel 25) is somewhat greater than the distance between two tool joints, so that at least one of two successive constricted passages is at all times closed either by the piston 4 or by the core barrel itself.

Fig. 2 shows a somewhat different embodiment of the present device, in which the piston or packer 4 forms a part of a separate hoisting device to be lowered into the drill pipe string.

'I'his hoisting device comprises a member 4I carrying jaws 31 hinged on shafts 38. A rod 33 having a lower thickened portion 34, and an upper reduced portion 32 passes through an axial opening in the upper part of the member 4I, the thickened rod portion 34 being located below said opening. A tube 3I surrounds the upper reduced rod portion 32 and carries externally the packer or piston 4. A spring 35 is provided around rod 33 and urges it upwards with regard to the member 4I, forcing the thickened portion 34 between the upper ends of the jaws 31 and the spring 35. When keeping thereby the lower ends of said jaws closed. v

The arrangement of all parts of the core barrel assembly proper is identical to that shown in Fig.1 1 below the thickened rod portion II (which is partially shown in Fig. 2). A knob-shaped fishing head 40 instead of the tube I0 is, however, attached to the top of the thickened rod II, and is adapted to be engaged by the jaws 31.

In operation, the following procedure may be followed when using the device shown in Fig. 2.

When the core has been drilled out, the hoisting device is pumped down the drill pipe string. The closed jaws come to rest on the knob 40, while momentum and Ithe downward pressure of the fluid forces the piston 4, tube 3|, and rod 32-33-34 further down against the action of the thickened rod 34 is detheir upper stroke pressed beyond the lower ends of jaws 31, the

lower ends of these jaws open and slide down jaws are locked in gripping engagement with the knob head 40, the barrel assembly and the hoisting device being then raised to the surface by the fluid pressure against the piston 4 as described above.

I claim as my invention:

1. In an apparatus for lifting cores through a drill pipe by iluid pressure, a core barrel within the drill pipe, means releasably locking the core barrel with the drill pipe, a piston above the core barrel in sliding internal engagement with Ithe drill pipe, rigid means connecting the piston to the core barrel, said means being capable of a limited axial stroke with regard to the core barrel, and being adapted on reaching the end of l to release the means locking the core barrel with the drill pipe and to cause the core barrel to follow .the piston when the latter is moved upwards by the ow of the uid'in the drill pipe.

2. In an apparatus for lifting cores through a drill pipe by fluid pressure, a core barrel within the drill pipe, means releasably locking the core barrel with the drill pipe, a piston above the core barrel in sliding internal engagement with the drill pipe, valve means surrounded ,by said piston to permit a downward ow and to prevent an upward flow of the fluid in the drill pipe past said piston, rigid means connecting the piston and the core barrel, said means being capable of a limited axial stroke with regard to the core barrel, and being adapted on reaching the end of their upward stroke to release the means locking the core barrel with the drill pipe and to cause the core barrel to follow the piston when the latter is moved upwards by Ithe uid flow in the drill pipe.

3. In an apparatusfor lifting cores through a drill pipe by fluid pressure, a core barrel within the drill pipe, means releasably locking the core barrel in engagement with the drill pipe', a piston adapted to be pumped down into the drill pipe by a downward fluid flow, gripping means carried by said piston, means actuated by a downward iiuid flow in the drill pipe to cause said gripping means -to engage the means locking the core barrel with the drill pipe, and means actuated by an upward fluid flow in the drill pipe, and comprising said gripping means, adapted to release the means locking the core barrel from engagement with the drill pipe, and to cause the core barrel to follow the piston when the latter is moved upwards .by the fluid flow in the drill pipe.

4. In an apparatus for lifting cores througha. drill pipe by fluid pressure, a core barrel within the drill pipe, means releasably locking the core` barrel to the drill pipe, a uid passage around the core barrel in communication with the inside of the drill pipe, means to pass a downward fluid ow through the drill pipe and said passage, means to reverse the direction of said flow, means within the drill pipe above the core barrel closing said drill pipe to an upward fluid ow, said means being actuated by a reversal of fluid ilow to release the means locking the core barrel to the drill pipe.

5. In an apparatus for lifting cores through a drill pipe by fluid pressure, a core barrel Within the drill pipe, means releasably locking the core barrel with the drill pipe, a fluid passage between the core barrel and the drill pipe, a Valved piston above the core barrel, the valve of said piston being adapted to remain open during a downward flow of the uid through said passage and to close when the direction of said flow is reversed, the closing f said valve automatically causing the piston to release the means locking the core barrel to the drill pipe.

ALPHONS GERARD HUBERT STRAATMAN. 

